Rosneft is also acquiring the other half of TNP-BP, Russia's third-largest crude producer, from BP for cash and stock in a deal worth $27 billion which will make the British company a major shareholder in Rosneft.

Rosneft, headed by Igor Sechin - a close ally of President Vladimir Putin, is now confronted with the task of combining the operations of two major producers while also implementing a raft of exploration deals concluded earlier with BP rivals.